In research on innate contraints on vocal learning, avian species have been identified that learn selectively, accepting conspecific vocalizations as models, and rejecting alien ones. New techniques of sound analysis and synthesis, developed on a small computer, will be used to specify acoustic features on which innate discriminations are based. Predispositions of subjects to extract clusters of notes as coherent "syllables" will be studied as an unusually clear and accessible case of natural perceptual categories. Having proved that acquisition of information at the syllabic and the syntactical levels involves separate processes, a program of research is proposed on the developmental basis of these longer-term aspects of temporal patterning of vocal behavior. Contributions of auditory feedback from production to this process will be analyzed. In parallel with laboratory studies on vocal perception and production in individuals reared under highly controlled conditions, field research will explore the nature and causes of enrichment of the perceptual processing of vocal sounds during the first year of life. Special emphasis will be placed on the role of self stimulation in the development of species song recognition. The importance of stimulation by vocalizations that share learned features with an individual's own productions will be investigated. Our aim is a synthesis of the interplay of innate and environmental influences in the development of perceptual processing of the complex acoustic signals used in avian communication.